This invention relates to generation of electricity and generally generation of electricity in autonomous systems.
Any generator requires a source of energy. In an aspect of this invention, the source of energy is the energy “freely” available due to an object already in motion. That is if the object is propelled by some means or in motion due to external forces which includes natural forces such as wind and waves or excess mechanical energy from the industrial machinery.
By motion is understood some relative movement of objects caused by vibrations, rotations, linear movements and acceleration.
WO 2012/164545 discloses a device for energy harvesting from an impact by using a piezoelectric MEMS scavenger comprising at least a gear with teeth driven by an inertial mass system and a piezoelectric transducer located next to the gear. In a potential application is the impact-type piezoelectric energy harvester array integrated with a commercially available mechanical watch mechanism consisting of an oscillating mass and a multi-toothed gear wheel. Motion causes the heavy mass to move and mechanical energy recovered from the oscillating mass will be converted into usable electrical energy by the piezoelectric harvester.
A generator based on piezoelectric harvesting will often be used in application where it is not possible to change a battery and where the wanted lifetime of the application is longer than what can be achieved by any battery. A mechanical contact between the gear and the piezoelectric harvester as described above will overtime cause wear and tear of the gear teeth and the tip of the piezoelectric harvester which will limit the lifetime of the generator. One aspect of this invention is to avoid the wear and tear due to the mechanical contact and thereby prolong the lifetime of the generator.
In particular, the invention relates to the generation or harvest of energy from movements at low frequencies and harvest over longer periods of time. However, the invention is not limited to such low frequencies although movements or vibrations of that type provide the most common situations.
Another aspect of the invention is to reduce the technical efforts needed to arrange a generator to produce energy or harvest energy. Thus, another object is to reduce complexity of such arrangement.